Arc torch push starting



1959 T. B. REED ETAL 2,898,441

- ARC TORCH PUSH STARTING Fi led July 3, 1957 Wafer Gas " Watgr IINVENfORS THOMASB. REED I 5'2 BY MART|NT.SMlTH,JR.'

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,4 TTORNEV nited States Patent 6 ARC TORCH PUSH STARTING Thomas B. Reed,Danville, and Martin T. Smith, In,

Indianapolis, Ind., assignors to Union Carbide Corporation, acorporation of New York Application July 3, 1957, Serial No. 669,785

*1 Claim. (Cl. 219-75) This invention relates to are torch pushstarting, and more particularly to method and apparatus for striking thearc and initiating the operation of the arc torch according to thecopending applications of R. M. Gage Serial No. 524,353 and Serial No.539,794.

The wall-stabilized arcs of transferred and non-transferred arc torchprocesses have previously been initiated by superimposing a highfrequency potential onto the DC. or AC. potential applied between theelectrodes. This procedure has several major disadvantages: it requiresa separate, expensive source of high frequency power; it requiresadditional insulation in the torch apparatus; and it interferes withradio and television reception in the immediate vicinity. In somecommercial applications of the arc torch process the high frequencypower has been rendered inefiective for are initiation due toconductance by minerals in the torch cooling water.

The main objects of the present invention are to avoid the difficultiesreferred to above, and to provide method and apparatus to employrelative motion of structural parts for the starting expedient.

A relatively simple solution has been found for starting arc torchprocesses which eliminates high frequency power. This novel procedureinvolves touching the torch inner electrode to the torch nozzleelectrode and then retracting it to form the arc. In the case of thenontransferred arc torch process the resulting are is the main processare. In the case of the transferred arc torch process the resulting arcbecomes the pilot are which initiates the main arc from inner electrodeto workpiece. This procedure is unobvious since prior art teaching wouldlead one to predict that touch starting would erode the nozzle electrodedue to resistance heating and are pitting. This erosion was found to benegligible.

The present models of the arc torch employing this principle use ametallic spring to retract the inner electrode from the nozzleelectrode. Future models could possibly employ a magnetic retractmechanism operated on electromagnetic forces produced by the weldingcurrent input.

Different arc shielding gases, such as argon, hydrogen, nitrogen, andhelium, require difierent potentials for are initiation. The push-startmethod enables positive starts to be obtained in any gas providedsufficient power is available to maintain the arc.

The accompanying drawing shows an'arc torch apparatus embodying theprinciples of the subject invention;

Early models placed the retract spring near the lower end of the innerelectrode. This position was found to be unsatisfactory since the heatfrom the arc aifected the the spring at the upper end of the innerelectrode and have operated quite successfully.

The torch shown in the drawing comprises a body having a lower anodeportion 10 and an upper cathode portion 12, secured together in axiallyaligned relation. The cathode portion comprises insulation molded abouta metallic insert 14 which has a central depending cathode coolingsleeve 16. Permanently secured in an axial bore in the upper bodyportion 12 is a push start sleeve or barrel 18, preferably silversoldered at the top of the insert 14. and at the bottom of the sleeve16.

The lower anode body portion 10 is constructed of metal, preferablyaluminum, brass or stainless steel, having a central bore aligned withthe upper body bore but of larger diameter to receive a centering sleeveof insulation having a radial flange 22 interposed between the upper andlower bodies. A plastic pin 24 passes through the flange intoregistering holes in these bodies. An insulating connecting ring 26 isscrewed onto the cathode body 12, and has an internal shoulder receivinga retainer ring 28 screwed onto the anode body 10.

The bottom of the anode body It is counterbored to receive a nozzleanode 30, and to form an annular cooling jacket 32 therearound. Theanode 3b is secured in position by a retaining cap 34 screwed onto theanode body 10 and compressing an O-ring packing 36. The anode nozzle Sithas a central bore 38 with a conical'top entrance 40. This anode nozzleis constructed of metal, preferably copper, and may have an internaltungsten insert.

Cooling water inlet and anode connection 42 is connected by a verticalbore 44 to the annular anode cooling jacket 32. A vertical bore 46 onthe opposite side connects the jacket 32 to a cross bore 48communicating with the cathode cooling sleeve 16. The opposite end ofthe cross bore 48 is the cooling water outlet and cathode connection 56.Shielding gas enters at inlet 52 and fills the annular space below thecentering sleeve 20 and surrounding the barrel 18 and passes through theconical entrance 4i) and out through the bore 38.

The barrel 18 extends from the top of the body 12 down close to thenozzle 3t and is provided intermediate its ends with a set back plug 54screwed into a threaded intermediate portion thereof. A squarecross-section setback rod 56 slides through a square cross-section holein the plug 54 and carries therebelow a cathode collet 58 secured to therod and slidable therewith in the barrel 18. A cap nut 66 secure s astick electrode cathode 62 preferably of tungsten in the collet 58. Theset back rod 56 extends up near the top of the body 12 to receive a pushbutton 64 slidable in the barrel 18. A coil compression spring 66surrounds the rod 56 between the push button 64 and the plug 54.

Rotation of push button 64 results in rotation of set back rod 56 andset back plug 54. This causes plug 54 to move up or down depending upondirection of rotation. Compression of spring 66 causes push button 64and consequently rod 56, collet 58 and electrode 62 to follow the axialmotion of plug 54. It is thus seen that the arc length between end ofelectrode 62 and nozzle electrode 30 can be easily adjusted by rotationof push button 64.

The are is initiated by pushing button 64 until electrode 62' comes intoarcing relationship with nozzle electrode Patented Aug. 4, 1959 30 andthen releasing pressure to allow spring 66 to retract electrode 62 topreset position.

What is claimed is:

Apparatus for starting an arc torch having a barrel, an electrode holderin said barrel and connected to a source of current, and an arcWall-stabilizing nozzle insulated from said electrode holder andconnected to said source, which comprises a plunger slidably mounted insaid barrel and from which said electrode holder depends, a push buttonslidable in top of said barrel for pushing said plunger and rod to bringthetelectrode tip into starting relationship with said arcwall-stabilizing nozzle, a coil compression spring engaging said buttonfor retracting said electrode tip from starting relationship, and a setback plug for adjusting retract distance of said electrode tip from saidarc wall-stabilizing nozzle.

References Cited in the file of this patent UNITED STATES PATENTS

